java - map 缩小作业以继续播放

Question

我有一个巨大的文本文件，其中包含文本数据。文件的每一行包含12个字符的数据。我需要使用map reduce作业从该文件中找到5个字符的子字符串。

输入文件。

abcdefghijkl
kahfdjshjsdh
sdfkjsdjkjks

搜索值

cdefg

'cdefg'可以出现在文件中的任何位置。它可以分为两行。所以我不知道如何创建当前行的后两个字符和下一行的后3个字符的映射。

Answer 1

I have a file containing lines of 12 characters and I want to find 5 character of string from that file. In Mapper I am getting 12 character of line and can create two maps of 5 character and left 2 character and want to get next 3 character from next line and want to create map of it. So in reducer I can compare that maps with my string.

您可以将所有行连接在一起，然后可以用5个字符拆分结果，请检查此 Splitting a string at every n-th character:

abcdefghijklkahfdjshjsdhsdfkjsdjkjks
[abcde, fghij, klkah, fdjsh, jsdhs, dfkjs, djkjk, s]

您可以从这段代码中启发解决方案:

File file = new File("myFile.txt");
try {
    Scanner scanner = new Scanner(file);
    String result = "";
    while (scanner.hasNextLine()) {
        String line = scanner.nextLine();
        result += line;
    }
    System.out.println(result);
    //here you can use this array
    String spl[] = result.split("(?<=\\G.....)");

    System.out.println(Arrays.toString(spl));
} catch (FileNotFoundException e) {
    e.printStackTrace();
}

输出

abcdefghijklkahfdjshjsdhsdfkjsdjkjks
[abcde, fghij, klkah, fdjsh, jsdhs, dfkjs, djkjk, s]

编辑

I Want to create map like this abcdefghijklkahfdjshjsdhsdfkjsdjkjks [abcde, bcdef, cdefg, defgh... ]

您可以这样解决此问题:

String str = "abcdefghijklkahfdjshjsdhsdfkjsdjkjks";
List<String> list = new ArrayList<>();

for (int i = 0; i < str.length()-4; i++) {
    String s = "";
    for (int j = i; j < i+5; j++) {
        s+=result.charAt(j);
    }
    list.add(s);
}

输出

[abcde, bcdef, cdefg, defgh, efghi, fghij, ghijk, ...., djkjk, jkjks]